1. Field of the Invention
The present invention relates to a biodegradable plastic and to articles made therefrom. The invention further relates to a method of producing a biodegradable plastic.
2. Background Information
The worldwide popularity of and use of plastic is in large part due to the indestructible nature of plastic. This same characteristic that makes plastic so attractive has lead to serious environmental problems which must now be addressed. The indestructible nature of plastic has lead to disposal problems. In a landfill, a standard polyethylene bag could take 300 to 400 years to be broken down. Landfills are overflowing as accumulating plastics are not degraded. As the garbage piles up in landfills and plastic debris litters the world's oceans, beaches and highways environmental concerns are growing. Innovative ways of reducing the accumulating plastic waste are required.
Plastic comprising polyethylene polymers consist of long chains of carbon atoms, each flanked by two hydrogen atoms. These polymers are tightly intertwined, creating a surface impenetrable to the decay bacteria that are normally responsible for breaking matter down to water, carbon dioxide and humus, or soil compost.
In response to waste disposal problems there has been a demand for biodegradable plastics. In an attempt to meet this demand, blended plastics have been created where synthetic polymers are mixed with naturally occurring polymers such as starch, cellulose or wood. Synthetic blends such as these allow bacteria to colonize on the natural polymers and once established, attack the previously inaccessible plastic polymers. Products using blends of starch and synthetic plastics are commercially available. Garbage bags comprising plastic polymers coated with cornstarch are sold by Archer Daniels Midland Co. in Decatur, Ill. and St. Lawrence Starch Co. in Canada.
Another approach to the creation of biodegradable plastics involves the use of bacterially synthesized plastics. These bacterial plastics are more palatable to other microorganisms than synthetic plastics. The bacteria Alcaligenes eutrophus produces large amounts of a plastic polymer called poly-beta-hydroxybutyrate, or PHB. Huge quantities of A. eutrophus or genetically engineered bacteria, are cultivated and the PHB harvested. Several companies are pursuing the use of bacterially made plastics such as PHB.
The present invention is considered to provide a significant advance in biodegradable plastics.